#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int n, k;
    cin >> n >> k;
    ll x[n+2];
    x[0] = -1e18; x[n+1] = 1e18;
    srep(i,1,n+1)cin >> x[i];
    ll a[n+2];
    a[0] = 0; a[n+1] = 0;
    srep(i,1,n+1)cin >> a[i];
    
    
    ll ma = x[k] + a[k];
    ll mi = x[k] - a[k];
    int r = k;
    int l = k;
    while(true){
        if(x[r+1] <= ma){
            ma = max(ma, x[r+1] + a[r+1]);
            mi = min(mi, x[r+1] - a[r+1]);
            r++;
        }else if(mi <= x[l-1]){
            ma = max(ma, x[l-1] + a[l-1]);
            mi = min(mi, x[l-1] - a[l-1]);
            l--;
        }else{
            break;
        }
    }

    int ans = r - l + 1;
    cout << ans << endl;
    return 0;
}